Vulcanization of rubber



Patented Nov. 30, 1937 UNITED STTES PATENT OFFICE 2,100,370 VULCANIZATIQN or RUBBER Ira Williams, Woodstown, N. J., assignor to E. I. g du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application May 18, 1935, Serial No. 22,171

12 Claims. (Cl. 18-53) This invention relates to the vulcanization of term "an acidic type sulfur containing accelerarubber and more particularly to the control of tor, I mean those containing the groups the activity of accelerators employed in the vulcanization.

S v; It has been recognized that certain types of or u 5 accelerators of vulcanization become much more S H active in the presence of various chemical activating agents. In general, it is known that accelerators which contain sulfur and which are of Whwh the mereepto a y e thiazo es. t d 19; acidic or which 1 hydrolyze to produce salts substituted di-thiocarbamates and derivatives of 0f thio acids or mercaptans will become more these which result from replacement of h effective in the presence of basic materials such f u of the f m h corrf3spond' as ammonia or diphenyl guanidine. The increase mg thiazole or di-thiocarbamic ac1d are illustrain activity, when produced in this manner, takes 5. place at 10W temperature as well as at the usual By the term Salt of an inorganic acid and an Vulcanizing temperatures so that compounds aromatic amine, I mean those salts which are celerated with the combination of acidic sulfur formed by the reactlon of ac1d 9' containing accelerators and basic organic matem SECQHdarY tertla'ry amme' Whfle rials become very troublesome due to vulcanizathere IS dlfieliertce m as to Whether tion during processing or during storage Nev} or not dlaryl guamdines are amines, they are so 20 Ous to being processed considered by me in the present case and are to Numerous material have been proposed for be understood to fall within the term aromatic controlling the activity of accelerators and the 32323 3223231 2 iig g gigig gi 215 effectiveness of acids such as benzoic, phthalic, generally be preferred Among these, those 25 and salicylic is generally known. Such products as diphenyl guamdine acid phthalate and other whose salts have proved to be the most satisfachalf salts of dibasic organic acids which still f fi1 $g figgfi i ggig fg gz conta'm free cafrboxyl 5 have also been either the neutral or acid salts but the neutral Posed as confbmed actlvators P salts will generally be preferred. In the follow- 30 It'is'an oblect of the Present mventl-on to ing examples, the compounds will be the neutral vide a class of compounds as activators for acidic salts except where th i indicated, ype Sulfur Containing ato s. A furth Among the inorganic acids which have proved object is to provide a class of compounds which to be particularly satisfactory there may be men- 35, will more effectively retard vulcanization by tioned hydrochloric acid, sulfuric acid and orthoacidic sulfur containing accelerators at low temphosphoric acid. Chloracetic acid is a strong peratures but which will activate such acceleraa id l ly approaching h n nic acids in tors at the higher or usual vulcanization temstr a d properties Its s ts s y apperatures. A still further object is to provide a preach the salts of the inorganic acids in prop- 9 method for controlling the vulcanization of ruberties and 9550161103 and may be considered to be 40 her. Other objects are to provide new composi- Substantial equivalents of the inorganic acid tions of matter and to advance the art. Still Saltsother bj ct W111 appear her i ft In order to more clearly illustrate my inven- These objects may be accomplished in accord tion, the preferred modes of carrying the same ance with my invention which comprises incor- Into 'efiect and the advantageous results 0 be porafing in rubber prior to vulcanization an obtained thereby, the following examples are acidic type sulfur containing accelerator and, given:

as a vulcanization controlling agent, a salt of an Example 1 59 i organic acid and an aromatic amine. By the I A base compound was milled which consisted 9 of 100 parts of rubber, 25 parts of carbon black, 5 parts of zinc oxide, 3 parts of sulfur, 3 parts of stearic acid and 0.5 part of mercapto benzothiazole. To this compound was added 0.5 part of the activator to be tested. The results of physical tests, after being vulcanized at both 227 F. and 287 F., are shown in Table 1.

Example 3 A base compound was milled which consisted of 100 parts of rubber, 25 parts of carbon black, 5 parts of zinc oxide, 3 parts of sulfur, 3 parts of stearic acid and 0.5 part of diphenyl guanidine sulfate, (C13H13N3)2H2SO4. This was accelerated with 0.5 part of benzothiazyl disulfide, with 0.5

It will be noted that the last three compounds which fall without the scope of my invention do not have the desirable properties of the other compounds.

part of benzothiazyl furoyl sulfide prepared by treating the sodium salt of mercapto benzothiazole with furoyl chloride and with 0.5 part of the cadmium salt of mercapto benzothiazole. The results are shown in Table 3.

Table 3 Cured at 227 F. Cured at 287 F. M t 1 Minutes a eria vulcanized LbsJm Lbs./in. Lbs/in at 500% at break at 500% at break elong. elong.

- 30 Not cured 2600 3800 Benzothiazyl-dlsulfide 60 N t 3 300 3650 30 o cure 2 50 3425 Benzothmzyl furoyl sulfide. 60 325 550 2425 3350 Cadmium salt of mercap- 30 Not cured 2000 3850 tobenzo thiazole 60 475 700 2500 3675 Example 2 Example 4 A base compound was milled which consisted of parts of rubber, 25 parts of carbon black, 5 p arts of zinc oxide, 3 parts of sulfur, 3 parts of stearic acid and 0.5 part of a-naphthylamine hydrochloride 'lo this compound 0.5 part of various mercaptothiazoles were added and the compounds were vulcanized at 227 F. and 287 F. The data are shown in Table 2.

A base compound was milled which contained 100 parts of rubber, 25 parts of carbon black, 5 parts of zinc oxide, 3 parts of sulfur, 3 parts of stearic acid and 0.5 part of the cadmium salt of mercapto benzothiazole. This compound was activated with 0.5 part of aniline sulfate and with Table 2 Cured at 227 F. Cured at 287 F. M t 1 Milltiutes a one vu canl'zed Egg-63 Lbs/in! Lbs/in! elong. at break along at break 1 .mercapto b naphtho- 30 Not cured 1200 1550 thiazole 60 Not cured. 1525 1700 1 mercapto methyl 30 Not cured. 1725 2925 benzo-thiazole 60 1775 2050 1 ignerclapto a naththo- 12120 e 3 1 1 mercapto 5 methyl I 30 Not cured 2000 2875 benzo-thiazole 60 350 2125 2650 0.5 part of diphenyl guanidine sulfate. The results are shown-in Table 4. v

From these various examples, it will beapparent that the compounds of my invention are Curedat 227 F.

' Cured at 287 F.

Minutes vulcan- Material 9 ized Lbs/in. at 500% elong.

Lbs/in. at break Lbs/in. at 500% elong.

Lbs/in. at break Aniline sulfate Diphenyl guanidine sulfate.

30 Not cured 25 Not cured 325 Example 5 A compound composed of parts of rubber, 5 parts of zinc oxide, 25 parts-of carbon black, 3 parts of sulfur, 3 parts of stearic acid and 0.5 part of thebarium salt of mercapto benzothiazole was treated with aniline sulfate and with diphenyl guanidine sulfate. The results of vulcanization tests are shown in Table 5.

Table. 5

much more efiective' than the salts of other bases and than the salts of organic acids in producing the so called trigger action effect. That is, with the use of these compounds of my invention there is less danger of scorching or prevulcanization during processing than with other somewhat similar compounds.

Inorganic salts of other primary, secondary and Cured at 227 F.

Cured at 287 F.

Material Lbslim7 at 500% elong.

at break ./in. at 500% elong.

Lbs/in. at break sulfide Tetramethyl thiuram disul- 30 V fide Not vulcanized Not vulcanized 30 Aniline sulfate Diphenyl guam'dine sulfate- 60 Example 6 A compound containing 100 parts of rubber, 5 parts of zinc oxide, 25 parts of carbon black, 3 parts of sulfur, 3 parts of stearic acid and 0.5 part of aniline sulfate was treated with 0.2 part of tetramethylthiuram monosulfide and with 0.2 part of tetramethyl thiuram disulfide. The results of physical tests are shown in Table 6.

Table 6 Cured at 227 F.

Cured at 287 F.

Minutes vulcanized Material LbSJmJ at 5007 elong.

at break at 500% along.

Lbs./in. at break Tetremethyl thiuram mono- Example 7 Table 7 Cured at 227 F. Cured at 287 F.

Minutes Vulcanized Lbs/in! at Lbs./in. 500% elong.

LbsJinJ at break Lbs/in] 500% elong.

at break ticularly the diarylguanidines such as diorthotolyl guanidine and the like. Also, the aryl groups may contain one or more alkyl groups such as methyl, ethyl, propyl, butyl, octyl and the like.

While the above examples illustrate some of the compounds which may be employed and some of the variations and modifications which may be made therein, it will be apparent to those skilled in the art that many other changes and variations may be made without departing from the spirit of my invention. Accordingly, the scope of my invention is to be limited solely by the appended claims construed as broadly as is permissible in view of the prior art.

I claim:

1. The method of vulcanizing rubber which comprises incorporating in a rubber mix an acidic type sulfur containing accelerator and diphenyl guanidine sulfate.

2. The method of vulcanizing rubber which comprises incorporating in a rubber mix a 1-mercapto-arylene-thiazole accelerator and diphenyl guanidine sulfate.

3. Rubber having incorporated therein an acidic type sulfur containing accelerator and diphenyl guanidine sulfate.

4. Rubber having incorporated therein a l-mercapto-arylene-thiazole accelerator and diphenyl guanidine sulfate.

5. The method of vulcanizing rubber which comprises incorporating in a rubber mix an acidic type sulfur containing accelerator and a diaryl uanidine sulfate.

6. The method of vulcanizing rubber which comprises incorporating in a rubber mix a 1-mercapto-arylene-thiazole accelerator and a diaryl guanidine sulfate.

7. Rubber having incorporated therein an acidic type sulfur containing accelerator and a diaryl guanidine sulfate.

8. Rubber having incorporated. therein a 1-mercapto-arylene-thiazole accelerator and a diary] guanidine sulfate.

9. The method of vulcanizing rubber which comprises incorporating in a rubber mix l-mercapto-benzothiazole and diphenyl guam'dine sulfate.

10. The method of vulcanizing rubber which comprises incorporating in a rubber mix benzothiazyl disulfide and diphenyl guanidine sulfate.

11. Rubber having incorporated therein l-mercapto-benzothiazole and diphenyl guanidine sulfate.

12. Rubber having incorporated therein benzothiazyl disulfide and diphenyl guanidine sulfate.

IRA WILLIAMS. 

